1. Field of the Invention
This invention relates to drive assemblies and in particular to means for minimizing friction drag losses in the movement of rotary drive assemblies through a body of lubricating and cooling fluid.
2. Description of the Prior Art
In one form of drive assembly used in crawler-type vehicles, the power train utilizes beveled gears and a complementing pair of steering clutches and brakes for effecting the individual drive of endless traction belts or chains normally provided on opposite sides of the vehicle. Large forces are generated in the operation of the power trains as they are conventionally utilized to effect steering and the like by selectively disengaging the clutches to interrupt the flow of power selectively to the different belts or chains. Concurrently, selective braking of the nonpowered chain is effected. Conventionally, the clutches and brakes are of the friction type and it is necessary to provide constant lubrication and cooling thereof in the operation of the apparatus.
One conventional form of providing the lubrication and cooling fluid to the drive assembly, such as the clutch of the power train, is to dispose the clutch to move through a body of refrigerating and cooling fluid carried in a subjacent sump. A substantial portion of the clutch is caused to pass through the collected fluid to provide the desired lubricating and cooling function.
A problem arises in such structures in that the clutch assembly includes securing elements, such as cap screws, which are utilized to secure different portions thereof together and which, during the movement of the clutch through the lubricating and cooling fluid, cause a power loss as a result of the friction drag produced by the cap screws as they move through the fluid.
One attempted solution to this problem is illustrated in U.S. Pat. No. 3,477,547 of Ralph H. Kress et al., owned by the assignee hereof. Therein, friction between the moving members of the drive assembly and the lubricant fluid is reduced by reducing the amount of lubricant so that during high speed rotation, centrifugal forces retain the fluid lubricant about the periphery of the gear housing. Angled tubes are provided for collecting lubricant from the housing and directing it inwardly onto the gears. It has further been known to provide, in connection with such large diameter beveled gears, a shroud of shallow depth to which a small portion of the oil returns in the operation of the gears. The gears are isolated from the main volume of coolant oil in the final drive case, and the main supply tends to remain separated from the rapidly rotating teeth of the gear.
While minimizing the amount of lubricant contacted by a moving drive assembly is efficacious in minimizing drag, it limits cooling of the drive assembly as when the drive assembly is utilized as discussed above in such high force applications as braking and de-clutching of tractor chain power drives.